Light-polarization films or polarizers are major components liquid crystal displays (LCDs) and other liquid crystal (LC) devices. Commercial polarizers are usually based on polyvinyl-alcohol-iodine (PVA) films of 150-400 μm thick. These polarizers are generally placed on the external glass surfaces of the LC cell and require protective films (e.g. cellulose triacetate or cellulose acetate butyrate). The fabrication of such known commercial polarizers is rather complicated and expensive. Recently, to improve the cost-effectiveness, there have been proposals to fabricate the light polarizers by printing or photo-alignment technologies.
In U.S. Pat. Nos. 5,739,296 and 6,049,428, polarizing films are formed from dyestuffs, which have stable lyotropic liquid crystalline phases in a wide range of concentrations, temperatures and pH-values. In a sheared flow, the lyotropic liquid crystal molecules are self-assembled and oriented preferentially in connection with the flow direction. When the proper preparation conditions are met, a well ordered solid phase of the lyotropic liquid crystal is formed. In certain cases, the order parameter as a measure of this alignment effect is high, so that this material is suitable for the fabrication of polarizers. To create this sheared flow, rollers and blades have been suggested.
To minimize any defects due to the shear flow alignment, a photo-alignment technology to prepare the thin photo-patterned polarizer has been proposed [V. Kozenkov et al, SID'00 DIGEST, p. 1099]. Since this is a non-contact method, the particulates and static charges generated can be in principle eliminated. In addition, the cross contamination problems can be minimized. With a birefringent mask, this technique makes the fabrication of multi-domain structures more cost-effective for the wide viewing-angle LCD applications.
There are various methods known for forming polarizing materials. One such method described in JP 2001-305526 requires the physical stretching of a substrate in order to induce polarization. It can be difficult to physically manipulate a substrate with precision, and stretching a substrate also means that it is hard to accurately create a substrate with a predetermined pattern of polarization. Further, this method does not give anisotropy of birefringence.